Galaxy:	Unknown
Quadrant:
Sector:	Unknown
Star System:	Unknown
Stars:	None
Known Planets:	None
Class:	Unknown

A classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics.

The most popular stellar classification system on Terra, thus becoming Earth Starfleet standard (2065 to 2161 CE) and Federation standard (since 2161 CE) later, is described below. It was developed by Annie Jump Cannon of the Harvard College Observatory from 1915 to 1924 CE while she and her colleagues were ordering 225,300 stars into stellar spectra of types O, B, A, F, G, K and M into what was published as the Henry Draper Catalogue shortly after. This classification inspired the mnemonic phrase "Oh Be A Fine Girl/Guy—Kiss Me (Right <Smack> Now)!" still taught to astronomy students today.

The Hertzsprung-Russell diagram (HRD) relates stellar classification with absolute magnitude, luminosity, and photospheric temperature.

Class	Characteristics	Color	Photospheric Temperature (K)	Examples
O	Ionized helium (He II)	blue	28000–50000	Mintaka
B	Neutral helium (He I), Balmer series hydrogen	bluish white	9900–28000	Rigel, Spica
A	Hydrogen, calcium (Ca II)	white	7400–9900	[[acamar]], Sirius, Vega
F	Calcium (Ca II), metals	yellowish white	6000–7400	Canopus, Procyon
G	Calcium (Ca II), iron and other metals	yellow	4900–6000	Capella, Sol (G2)
K	Large share of metals, later titanium oxide	orange	3500–4900	Arcturus, Aldebaran
M	Titanium oxide	reddish orange	2000–3500	Antares, Betelgeuse, Kapteyn's Star
Subclasses
R	Cyan (CN), carbon monoxide (CO), carbon	reddish orange	3500–5400
S	Zinc oxide	reddish orange	2000–3500
N	Carbon	red	1900–3500